The U.S. Environmental Protection Agency is responsible for establishing limitations on vapor emission at gasoline refueling service stations. In order to determine whether the refueling systems meet these limitations, it is necessary to employ apparatus for collecting gasoline vapors emitted at the dispensing nozzles during gasoline refueling and for measuring and displaying the amount of emission. Various test procedures and equipment for this purpose have been proposed in the Federal Register (40 FR 197, Oct. 9, 1975), all of which have proved to be too complex and costly for the results obtained. For example, some previously proposed procedures have involved the use of specially modified nozzles, carbon adsorption devices, and other cumbersome and expensive equipment. In general, the previously proposed apparatus and procedures have been found to be unsatisfactory because they require an excessive amount of manpower, require a longer period of time to run the required tests, and involve the use of excessive amounts of equipment.